Question: Combine like terms to create an equivalent expression. $3.4-2.8d+2.8d-1.3$
Answer: Combine the ${\text{coefficients}}$ of the $d$ terms, and combine the ${\text{constant}}$ terms. $3.4-2.8d+2.8d-1.3$ $\phantom{=}{3.4}{-2.8}d+{2.8}d-{1.3}$ $=\left({-2.8}+{2.8}\right)\cdot d+{3.4}-{1.3}$ $=0\cdot d+2.1$ $=0+2.1$ $=2.1$ The simplified expression is 2.1.